Travel Time Of Finite Difference Simulation Of Wave Field Of Seismic Tomography Method And Application Of Research

Seismic tomography is used to study the 3-D seismic velocity structure andattenuation structure of earth by the seismic wave information obtained from a largenumber of passive earthquakes and artificial earthquakes. At present, seismictomography has been an important method and is widely used in geosciences research.The theory and method of seismic tomography has been analyzed and studied in thispaper. The progress of inversion theory and seismic tomography are also illustrated.Especially, finite-difference seismic tomography is analyzed and studied in detail.Moreover, the reliability of this method is verified by both forward and inversemodeling with several 3-D theoretical models.This study is a main part of Kunming seismic activated faults exploration project.Study region is from N24o52' to N25o12' and from E102o35' to E102o54'. Fourseismic profile lines form a rectangle in Kunming region. After careful selection ofsix-shot artificial earthquakes data, 780 Pg is obtained. Finite-difference seismictomography is used to image the 3-D velocity structure of shallow crust with thosedata. The extension in deep of main activated faults (Baiyi-Hengchong fault andPuduhe fault belt) surrounding Kunming city and its region in surface and shallow ofearth were illuminated. And then, several results are obtained:1. The pattern of velocity distribution shows that high velocity regions mainly liein east, north and west part of study region and low velocity regions mainly lie inmiddle and south part of study region. This is consistent with the geographicalsituation of study region.2. The relation between some faults and basin velocity structure is obvious instudy region. Puduhe-Xishan fault lies on the west edge of the basin and is situated onthe west edge of low anomalous velocity region in velocity distribution graphs at alldifferent depth. This indicates that this fault is a borderline fault of Kunming basin.On the west side of this fault, the north part is high velocity region;however, thesouth part is normal velocity region. Dividing line is the interjunction of this fault andMajie-Wulong fault. West-northwest and east-southeast Fumin-Chenggong faultapproximately parallels zonal low velocity abnormal region in the south of studyregion. Even though both of them are not completely same, they also have closerelationship.3. Baiyi-Hengchong fault locates at gently low velocity region in the east ofstudy region. No obvious velocity change is found at both side of this fault, whichshows the relation between this fault and velocity distribution is not obvious. It is alsosimilar to several other faults.4. North-east Majie-Wulong fault and Chejiabi-Dashuying fault traverse the lowvelocity region in the middle of study region. They control the distribution of locallow velocity in the middle of study region.